Anaphylaxis is a life-threatening medical emergency because of rapid constriction of the airway, often within minutes of exposure to the allergen. It is commonly triggered by insect stings and foods such as shellfish or peanuts. Call for help immediately. First aid for anaphylaxis consists of obtaining advanced medical care at once. Look to see if a device such as an Epi-pen is available - most people who know they have anaphylactic reactions will carry an Epi-pen with them. First aiders in many jurisdictions are now permitted to administer epinephrine in the form of an Epi-pen if the victim is unable to do so themselves. Check what the law says in your area.

Administering an EpiPen is not legal in all jurisdictions without proper training and certification.

EpiPens are the most common form of epinephrine auto-injectors, and are designed for ease of use. There are instructions in the tube with the auto-injector, but you should know how to use one ahead of time. They're designed to inject through clothes, so you don't have to remove the victim's pants - even if they're wearing a heavy material like denim. Whenever possible, the victim should inject themselves, but if they're unable to do so, you may be legally permitted to inject the victim.

Remove the auto-injector from the tube. One end has a black tip - this is where the needle will come out. Do not touch this tip! The other end has a grey cap. Remove the grey cap, hold the EpiPen in your fist, and press it firmly against the outside of the victim's outer thigh. There should be an audible click. If there is not, try again but pressing harder. Hold the auto-injector in place for 10 seconds. When you remove it, massage the area for 10 seconds, then replace the EpiPen into the tube needle end first to avoid any danger. When EMS arrives, they can dispose of it for you.